A more relevant question would be, is it feasible, and has anybody written it yet. IMHO: It is very feasible, except I can't recall any full-screen VST plugins; although I don't know that it would be difficult to do. As to has anybody written it yet? I'd say, I'm not seeing one yet; nor any such visual entertainment-oriented VST. The lack of other responses and my own superficial search lead me to suggest that a Winamp2/ffdshow or VST visualization plugin be written for use in Winamp, ffdshow and if written as a VST: also VST hosts.

surprised this has never been done, would be really cool to be able to do milkdrop with audio as it's being made/processed with FX. or some insane person could try to make a track without hearing it, just go by how the visuals change.

I also looked for a VST IRC plugin to no avail. if I could find these two things plus maybe a rudimentary web browser I would barely ever have to leave my DAW

Hey people! I see that I'm not the only one who thought about it. I love Milkdrop, I like to use it with linein;// thing to play live music and feed it with my guitar etc. Anyway there is one main problem, Asio4All (used with Presonus Studio One in my case) grabs all computer audio and Winamp can't move along with it. Another thing that comes to mind is that with multimonitor setup each instrument could have it's separate VST instance so we could have different visualisations for each instrument and control what is shown on separate windows along sound route (and if you put it on master in DAW it would dance to overall music, just like in Winamp)